This invention relates generally to restricted access RF communications systems and is particularly directed to a means and method for identifying and validating individual users of a repeater-type trunked radio system.
Trunked RF communications systems typically utilize a repeater approach in which a central repeater is responsive to incoming calls for retransmission to a remote receiver. Incoming calls generally include a coded portion which uniquely identifies the caller and/or the party to whom the call is directed. Once the transmitted message is received, either the central repeater decodes and retransmits the message to the intended receiver or the remote receiver decodes the retransmitted message. This selective accessing approach may be accomplished by any number of conventional techniques. For example, the retransmitted signal may be coded so as to result in the call up of only the intended receiver.
In these limited access communications systems it is, of course, highly desirable to restrict usage to only intended, i.e., paying, customers. Thus, it becomes essential in such systems to know, and be able to grant system access to, those who are qualified to use the system. This requires a real-time system monitoring and control function which is capable of not only instantaneously determining who is a qualified user, but of also either denying or granting access to the system depending upon the status of the communicator, which status may change frequently. In addition, this monitoring and control function should be capable of handling a large number of users as repeater trunk communications are becoming increasingly popular and more widely accepted.
Prior art user validation systems generally utilize a simple frequency averaging technique involving adding several frequency measurements and dividing by the number of measurements. This approach results in limited system security and possible erroneous user validation. The present invention is intended to provide an improved subscriber validation system for a trunked repeater communications system in which user identity and eligibility for system use are rapidly and accurately determined by means of a unique means and method for detecting and validating a user's code in providing a high level of communications systems security. While intended for use with the GE-MARC V Trunked Mobile Radio System, the present invention is not limited in its scope to use with this system but has application to any conventional restricted access communications system.